1. Field of Invention
The present invention relates generally to medical methods and devices. In particular, the present invention relates to methods and devices for applying energy to the urethra and the prostate to achieve volumetric tissue reduction.
A number of medical conditions affect the male urethra causing a variety of symptoms including painful or difficult urination, a swollen prostate, blood in the urine, lower back pain, and the like. Some of these conditions, such as prostatitis, are bacterial infections which can be treated with antibiotics and other drugs. Other conditions, however, such as benign prostatic hyperplasia (BPH) and prostatic carcinoma, result in enlargement of the prostate and obstruction of the urethra, sometimes leading to complete loss of bladder function.
Although various drug therapies for treating BPH have been proven to be effective, their effectiveness tends to be of limited duration, and often requires additional intervention such as surgical treatments.
Surgical treatment of BPH includes several variations of radical or partial prostatectomy involving complete or partial electrosurgical removal of the prostate. Prostatectomy constitutes the most invasive and effective treatment for the palliation of urinary flow obstruction secondary to constricting prostatic enlargement. It is still regarded by the American Urology Association (AUA) as the gold standard of care in the management of acutely symptomatic BPH, although its usage in urology practices has been rapidly declining due to the introduction of less invasive techniques. Open surgery-based radical prostatectomy is rarely employed in the treatment of BPH, being reserved almost exclusively for prostate cancer indications.
A prostatectomy may be achieved via open, laparoscopic, or transurethral approaches. The latter is preferred for a partial prostatectomy, which is typically performed in patients with acutely symptomatic BPH. Established versions of the technique include electrocautery-based transurethral resection of the prostate (TURP), transurethral vaporization of the prostate (TUVP), as well as transurethral incision of the prostate (TUIP), although the latter technique is used infrequently. In TURP, an electrosurgical loop is inserted into the urethra and used to remove excess prostatic tissue, whereas TUIP relies on cutting muscle adjacent to the prostate to relax the bladder opening to relieve difficulty in urination. TUVP was developed to produce comparable results to standard TURP while reducing procedural morbidity and hospitalization time. In TUVP, the electrosurgical loop is replaced with a roller ball capable of delivering sufficient energy to vaporize prostate tissue.
Over the last decade, medical device manufacturers have developed several minimally invasive (MI) directed energy-based techniques for BPH that are intended to reduce morbidity and complications with electrosurgical approaches, allow treatment in a more economical outpatient setting, and make it suitable for patients who fail drug therapy, but are not severe enough to warrant electrosurgical interventions such are TURP. Among these MI techniques are transurethral microwave thermotherapy (TUMT), RF-based transurethral needle ablation (TUNA), water-induced thermotherapy (WIT), as well as several laser ablation techniques using transurethral optical fibers such as interstitial laser coagulation of the prostate (ILC), holmium laser enucleation of the prostate (HoLEP), and photoselective vaporization of the prostate (PVP).
While generally successful, TUMP, TUNA, and WIT are inadequate to treat all patients and all conditions. In particular, patients having severe tissue intrusion into the urethral lumen resulting from BPH or prostatic cancer are difficult to treat with the above mentioned methods which rely on tissue shrinkage rather than resection. Thus, many of these patients will eventually require conventional surgical resection.
In contrast, HoLEP and PVP are capable of actively removing tissue by vaporization. However, HoLEP is limited by the long procedure time and the relatively high learning curve which has limited its dissemination.
Accordingly, the urological community has recently embraced the relatively technically less demanding PVP where a laser beam with output powers ranging from 60 to 120 W is directed from the urethra against prostatic tissue to achieve irradiance (power density) levels over a certain volumetric power density, referred to as a vaporization threshold, below which tissue coagulation rather than vaporization occurs. As the irradiance level increases above the vaporization threshold, tissue vaporization increases and coagulation decreases. However, the beam emitted from the probe in PVP systems is diverging. Therefore, the laser spot size enlarges with increasing probe distance from the tissue, and the power density decreases, reducing the rate of vaporization. Hence, in order to maximize the rate of tissue vaporization and thereby limit the extent of the zone of thermal damage characterized by tissue coagulation left after the procedure, the physician must steadily hold the fiber a fixed distance (e.g., 1-2 mm) away from the tissue and slowly scan the beam over the target tissue without varying the distance. As the procedure progresses, the tissue becomes carbonized and more difficult to ablate. Thus, a significant limitation of PVP is the decreasing rate of tissue removal as the procedure progresses, which dramatically increases procedure time, patient cost, and risk. Additionally, the effectiveness and duration of this procedure is highly dependent on the skill of the treating physician and the use of a very expensive high-power laser system.
Furthermore, most of the procedures described above require very high energies to coagulate and/or vaporize tissue, which can only be generated with large, high-power, and expensive equipment.
Additionally, current treatments of BPH are often associated with high risk of complications. For example, TURP is associated with retrograde ejaculation, post-operative irritation, erectile dysfunction, significant hematuria, and acute urinary retention and incontinence, among other complications. Post-treatment complications may be attributed to resecting, ablating, or otherwise damaging non-glandular tissues within the prostate-urethral region, such as the seminal vesicles, sphincter muscles, intra-prostate vessels, nervous tissues, or fibromuscular stroma. Additionally, treatment modalities that utilize selective thermolysis to ablate, coagulate, or denature targeted tissues to obtain sufficient reduction of prostate volume are likely to result in an extensive tissue zone of thermal damage. The consequences are the formation of edema and swelling of the heat-treated prostate tissue, often resulting in the inability to provide immediate symptomatic relief with the patient going into urinary retention and requiring post-procedure catheterization and hospitalization.
Furthermore, because the symptoms of prostatic disorders such as BPH often result in obstruction of the urethra, any trans-urethral prostatic treatment methods and devices are likely to be hindered by abnormal tissue occlusion. This is because the device may not be able to properly move within the occluded space to treat the desired area, thus preventing treatment devices from functioning properly or optimally. Additionally, abnormal tissue occlusion may also limit visualization of the treatment procedure and generally impedes optimal treatment.
For these reasons, it would be desirable to provide minimally invasive methods and devices which provide for enlarging the luminal area and/or volumetric resection of tissue surrounding the urethra. It would be particularly desirable if such methods and devices provided for heat-free removal of tissue, allowing tissue resection without inflicting thermal damage to tissue. It would be particularly desirable if such methods and devices provided for removal or destruction of such tissues surrounding the urethra where the removal or destruction products can be removed from the lumen to relieve pressure on the urethra, even when large volumes of tissue are being removed. Furthermore, it would be desirable for such methods and devices to minimize post-treatment complications by selectively resecting glandular tissue while leaving non-glandular tissue substantially undamaged. Additionally, it would be desirable for such methods and devices to expand the treatment region by creating a working space to enable better device movement and better visualization of the treatment region. Alternatively or additionally, the methods and devices should provide for anchoring of the treatment device relative to the urethra in order to provide a stable platform for treatment protocols. Methods and devices for performing such protocols should present minimal risk to the patient, should be relatively easy to perform by the treating physician, and should allow for alleviation of symptoms with minimal complications even in patients with severe disease. At least some of these objectives will be met by the inventions described below.
2. Description of the Background Art
Use of a transurethral endoscope for bipolar radiofrequency prostate vaporization is described in Boffo et al. (2001) J. Endourol. 15:313-316. Radiofrequency discharge in saline solutions to produce tissue-ablative plasmas is discussed in Woloszko et al. (2002) IEEE Trans. Plasma Sci. 30:1376-1383 and Stalder et al. (2001) Appl. Phys. Lett. 79:4503-4505. Air/water jets for resecting tissue are described in Jian and Jiajun (2001) Trans. ASME 246-248. US20050288639 described a needle injector on a catheter based system which can be anchored in a urethra by a balloon in the bladder. U.S. Pat. Nos. 6,890,332; 6,821,275; and 6,413,256 each describe catheters for producing an RF plasma for tissue ablation.
The use of lasers for cutting biological tissue is described in U.S. Patent Publication No. 20020128637 and for ablating prostate tissue is described in U.S. Pat. Nos. 5,257,991; 5,514,669; and 6,986,764. Pressurized water streams for effecting surgical incisions are described in U.S. Pat. Nos. 7,122,017; 5,620,414; and 5,505,729. The use of water or other fluid jets as waveguides for carrying a laser beam for cutting and other manufacturing operations is described in U.S. Patent Publication No. 20070278195, published Canadian application 2,330436 A1, PCT publication WO 99/56907, and U.S. Pat. Nos. 7,163,875; 5,902,499; and 5,773,791.
U.S. Pat. No. 6,960,182 describes using a liquid jet instrument to resect tissue such as the joint capsule of the knee, wherein a nozzle forms a liquid jet and the jet is received by a jet-receiving opening. U.S. Pat. No. 5,135,482 describes a hydrodynamic device for eliminating an organic deposit partially or completely obstructing a vessel of the human body. The patents do not disclose using a fluid stream to resect tissue within an enclosed tissue region such as the prostate-urethral region. U.S. Pat. No. 5,782,848 describes using a water jet to resect coagulated tissue. The patent does not disclose using a fluid stream to resect non-coagulated tissue or otherwise untreated tissue.
U.S. Pat. No. 5,207,672 describes compressing a portion of the prostate by using a balloon and ablating the tissue with a laser beam. The patent does not disclose expanding the urethra and then using a fluid stream to resect the tissue.
U.S. Pat. Nos. 4,560,373; 3,818,913; 4,913,698; 5,505,729; and U.S. Patent Publication Nos. 20090149712 and 20090157114 describe using a fluid stream to treat various tissues. The patents and patent applications do not describe using a fluid stream to resect tissue in an enclosed tissue region such as the prostate-urethral region. Various other aspects of fluid jet surgery apparatus such as pumps, applicators, and such are described in U.S. Pat. Nos. 5,037,431; 6,720,745; U.S. Patent Publication Nos. 20070129680, 20080038124, 20080243157, 20080221602, and 20090060764.
U.S. Patent Publication No. 20080097470 by Gruber et al. discloses the use of mechanical distension and fluid jet dissection in gynecological procedures. The application does not describe using a fluid stream to resect a volume of tissue. U.S. Patent Publication Nos. 20080188868, 20080249526, and 20090287045 disclose the use of fluid jet tissue resection, for example in laparoscopic procedures. As is commonly known, laparoscopic procedures create a working space in the abdominal cavity and the working space is not created inside the organ that is subject to surgery. The above mentioned publications do not describe inserting a device into an organ, creating a working space within the organ, and using a fluid stream to resect organ tissue.